Electrical switch



NOV. 9, 1948. A, KAVANAGH 2,453,231

ELECTRICAL SWITCH Filed Aug. 9, 1945 FIG. 2.

JNVENTOR. AKAI/MGH Patented Nov. 9, 1948 ELECTRICAL SWITCH Joseph A. Kavanagh, New York, N. Y., assigner to International Business Machines Corporation, New York, N. York Y., a corporation of New Application August 9, 1945, Serial No. 609,814

(Cl. 20G-16) 3 Claims.

This invention relates to electric switches and more particularly to that class known as a push button switch.

The primary object of the present invention is to provide an improved push button switch suitable for use in signaling systems.

An object is to provide a push button switch suitable for use in nurses'call systems and other systems employing annunciators, buzzers, and other signals, particularly signaling systems used in hospitals.

An object is to provide a push button switch which is relatively simple and easily operated.

An object is to provide a push button switch of the locking type arranged to lock in an intermediate operated position for the maintenance of a visible signal such as a light after the sounding of a momentary signal and the release of the annunciator target.

An object is to provide a push .button switch which is very simple and rugged in construction so as to be capable oi withstanding considerable abuse and capable of long life.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a longitudinal section showing the switch in normal position.

Fig. 2 is a side view partly in section showing the switch in the intermediate or locking position.

Fig. 3 is a side view with the casing removed and 'showing the switch in the fully operated position.

Fig. 4 is an end View oi! the switch as viewed from the right in Fig. 3. l

Fig. 5 is a wiring diagram illustrating the application oi' the switch to a typical nurses call system.

The casing for the switch is substantially bullet-shaped in outline and comprises what may be termed the base portion I0 and a cover II which may be screwed on a threaded shoulder Illa formed in the base i0. The cover II is provided with an opening IIar at its right hand end for the introduction of the extension cord which connects the switch to the bedside outlet when the switch is used in a nurses call system. The base III is formed with two parallel branches Illb which extend into the interior of the casing II to a point a little to the left oi the opening IIa to which point the branches Ib are integral the end of a metallic tubey I4 received in a longitudinal bore lud in the base I0. Also secured on the left-hand end of the tube I4 is the switch actuating ringer-piece or push-button I5 which has a reduced cylindrical portion or shank I5a sliding in the bore Ille which is concentric with the bore Ille and the tube I4. Also secured on the tube I4 tight against the bushing I3 is a metallic contact element I6. The bushing I3 and the contact element I6 thus are pushed to the right (Fig. 1) whenever the push-button I5 similarly operated.

The base I0 and the cover II preferably are formed of a suitable insulating material such as molded plastic and is shaped so that the switch may be easily held in the palm of the hand and the button I5 pressed with the thumb. The bushing I3 is roughly shaped like the frustum of a cone whereby, when the button I5 is actuated all the way to the right as described, the contact elements I2 will be spread apart and ride up upon the surface of the contact element I6 as shown in Fig. 3. In this position all of the contact elements I2 will be electrically connected together by the contact element. I6. Normally the bent ends of the contact element I2 press against the conicalr surface of the bushing I3 and thereby tend to cam said button and the contact I6 to the left, thus normally holdingthe contact I6 and the push-button I5 in the position of Fig. 1. The contact element I5A also is shaped like a frustum of a cone but its smaller lbase is somewhat enlarged at Ilia, the enlargement being formed as a conical surface which, with the larger conical surface, forms a shallow groove. In other words, the contact member I6 is shaped roughly like an hour glass with one of the sections of shorter length than the other. When the push-button I5'is operated to push the contact member to the position of Fig. 3 and released, the bent ends I2a, by pressing inwardly toward the longitudinal axis of the switch, causes the restoration of the button I5 which continues until the bent portions I2a strike the enlarged portion IBa and retain the contact member Il and the nnger piece II in the position of Fig. 2. In other words, when the push-buttonA is in this position, the spring pressure of the contact elements I2 tends to move the push-button a Ii and the contacts I. to the left and, if the push-button is released slowly or not too quickly, the push-button will be merely restored to the extent shown in Fig. 2 and will remain in that position. Thus. the push-button may be locked in an intermediate position in which it will remain until released holding circuits through contacts I2 and II.

' Release of the switch may be eected either by again pressing the button I5 to the right and releasing it quickly, as by flicking the button I5 with a finger, or the button may be positively pulled to the left from the position of Fig. 2 with the fingers.

Mounted in slots in the plug Ic on diametrically opposite sides of the longitudinal axis of the switch, between the slots for contacts I2, are two additional secondary contact members l1 which extend inwardly and are formed with bent portions Ila similar to the portions I2a These bent portions I1a engage dlametrically opposite sides of an insulating bushing I8 secured on the end of a rod Il which is loosely mounted in the bore of the tube I4. The bushing I8 is shaped approximately like an hour glass and is mounted alongside of a contact 2li shaped like a frustum of a cone and secured on the rod I9, means such as a nut being provided to clamp the bushing Il and the contact 2l together on the rod. The contact elements I1 thus coact with the assembly comprising bushing I8 and contact 2c in the same general way as the contact elements I2 cooperate with bushing I3 and contact It, except that in this case there is no intermediate enlargement like Ita and the conical surface of the contact 2t merges smoothly with the surface of the bushing I8.

When the button Il is pressed to the right to contacts I1 ride up on the conical surface of the contact 20 and electrically connect the contact elements I1. Inasmuch as the sleeve Il, the contact It, rod Il, and contact 2II are metal and in contact with each other the effect of pushing the button II to the right as described is to electrically connect together all of the contact elements I2 and I1. When the pressure on the button Il is released and the switch permitted to lock in the position of Fig. 2, the circuit through the contact elements I1 is broken owing to the fact that as the button I! moves to the left from the position oflFig. 3, the pressure of the contact elements I'I rst causes the rod I! and contact 20 to follow the bushing I3 to the left until the bent portions I'la reengage the bushing I8. With continued movement of the push-button I and parts connected thereto, to the left to the position of Fig..2. the assembly including the bushing I8, rod Il, and contact 2l is held by members I1 in the position of Fig. 2.

The application of the push button switch to a typical signaling circuit may be illustrated in Fig. 5 which shows the elements of a nurses call system suitable for use in either the private rooms or the wards of a hospital. In Fig. 5 the line wires of the signal system are designated A, B, C, of which Wires A and B are the main current supply wires from a. low voltage transformer 'I'. The third wire C may be the buzzer common for the annunciator board. In the present case, it is assumed that the board contains a light designated L in Fig. 5 for every bed or private room whereas S designates the buzzer which is common to all of the lights on the board. L2 may be a light located over or. adjacent the door to a private room to indicate to a nurse passing through the corridor that the patient needs attention. L3 may be used in wards where there may be provided a signal lamp Afor each bed or patient to notify the nurse which patient signaled for attention.

When the push-button I5 is pushed to the right as far as it will go, as in Fig. 3, four circuits are established simultaneously through the lights LI, L2, L3 and the buzzer S as follows: Line wire A, one of the Contact elements I2, the contact I6, rod I9, contact 20, a contact I1, wire C, and buzzer S, to the other line wire B. This draws the attention of the nurse to the call board if absent from the board but near enough to hear the buzzer signal. As soon as the pushbutton I5 is released and the switch permitted to assume the position shown in Fig. 2, the circuit to buzzer S is interrupted. A second circuit is established through the call iight LI on the board from the vline Wire A, a contact I2, contact I6, another contact I2, and lamp LI, to the line wire B. When the push-button switch is released and locks in the position of Fig. 2,

the lamp LI remains lighted and indicates on the call board the room or bed needing attention. In similar fashion the lights L2 and L3 are lighted and remain lighted as long as the switch remains in the position of Fig. 2.

It is thus possible for the nurse to tell immediately, whether she is at the desk or making rounds to patients, who requires attention and, as each patient is attended the nurse will restore the push-button switch in the manner disclosed above before leaving the patient.

It will be understood that there may be as many push-button switches as there vare beds or private rooms and the connections for all the switches to the wires A, B, and C will be the same but there will be an individual wire D from each push-button station to a lamp on the call board. In the case of private rooms with a single bed the lamp L3 may be dispensed with as it serves no useful purpose at the bedside. When the signal S is restored in a, ward, only one light LI is necessary at the nurses desk in which case all of the push-button switches will be connected in common to the wire D and the lamp L2 may be dispensed with. It will be seen that the pushbutton switch is adaptable to a variety of purposes in a call system.

One of the main effects of the push button switch described hereinis that the wear on the contact elements is more even and better contact is obtained by reason of the wiping action resulting when the button I5 is pressed and also arising from the fact that the cont-act elements I6 and 20 are free to rotate. In the use of the switch, the button I5 naturally will be rotated slightly from time to time thus causing different parts of the surface of the contacts I6 and 20 to rotate more or less. On account of the symmetrical arrangement and number of contact elements I2 and I1, the contact elements Il and 2l are automatically centered thereby simplifying their mounting. It is thus possible for a great deal of wear to take place in the switch elements before there is likelihood that it will fail to function properly. Thus the moving parts of the switch do not have to be made with great precision thereby reducing the cost of manufacture considerably. This arises from the fact that themoving parts are self-centering making it unnecessary to provide close tolerances in the moving parts or their mounting.

While there have been shown and described and pointed out the fundamental novel features of the invention, as applied to a preferred embodimentit will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operationmaybemadebythoseskilledinthe art without departing from the spirit of the invention. It is the intention therefore to belimited only as indicated by the scope of the following claims.

What is claimed is:

1. An electric switch comprising a contact element having a shape like an hour glass and an insulating bushing secured in axial alignment: therewith and having a shape like a frustum of a cone with its larger diameter the same as the diameter of the adjacent base of thecontact element, a pliuaiity of contact fingers symmetrically disposed about the axis of said insulating bushing and said contact member and Anormally coacting with the side of said insulating bushing to maintain the contact in open circuit position, said insulating bushing and contact element .being movable in the direction of their axis to carry said contact lingers into engagement with said contact and by coaction with the narrowest part of the contact element maintaining said contact in a closed circuit position with said contact members, said contact and insulating .bushing having an overtravel greater than necessary to establish electrical oontact'between said linger and said contact and a second contact means closed when said ilrst contact overtravels and opening when said contact moves to locking position, saidcontacti'ingeractingonsaidcontact to move said contacts to the locking position f 6 and a nger piece for actuating said iirst named contact to the overtravel position.

2. An electric switch comprising a contact member shaped like a cone and having a locking ridge disposed peripherally of one base of said cone, said contact member being movable along the axis of symmetry of said cone from an open circuit position to a first closed circuit position vpast an intermediate closed circuit position: a

an axis, oneY group of primary contact elements being spaced along said axis from the other group of secondary contact elements; and two contact members aligned on said axis, one for each group of contact elements, the contact members being movable from an open circuit position past an intermediate closed circuit position in which one of said contact members engages the primary contact elements to a terminal closed circuit position in which the other contact member engages the secondary contact elements, said iirst one of said members being shaped to coact with the primary contact elementspto hold said one contact member in the intermediate closed circuit position when the contact members are restored from said terminal closed position.

JosErH a. KAVANAGH.

- REFERENCES CITED The following references are of record in the 5 ille of this patent:

FOREIGN PATENTS ,Number Country Date '755,222 `France v Hay 8. i933 

